Is it possible to recover my photos?
It depends but I am really afraid the answer is no.
Are you opening the one and only sparsebundle on the TC??
I need to know what you did.
Prior to this, I backed up everything on my TC using Time machine.
That was the worst kind of backup you could have done.. a disk utility image or a bootable drive image is what you should have done.. for next time and other people reading.. TM backups are difficult to extract data from.. an image is direct one to one file..
I decided to erase everything and start over.
So you clean installed Yosemite??
Did you change the computer name?? If so your backups will be in a different sparsebundle.. as the UUID should have changed.
If you did some other sort of install.. or kept the same computer name.. and then continued to do Time Machine backups over the existing ones.. very bad things could happen.
I can only go back to a september date, (but nothing prior to the sept 18th even if I backuped up all summer long), where there are no signs of my old iphoto librairies.
My hope here is .. you changed computer names.. you are looking in the wrong sparsebundle.
I tried to use stellarinfo phoenix recover data but I don't know how to directly mount my TC so the software can't find it. I really care about my librairies since they are mainly my sons childhood...
Stop doing backups or anything to this TC right now.
But if you messed up the sparsebundle.. you waited far too long..
You should have migrated the user files immediately..
TM deletes files that do not exist on the Mac. Not immediately but after several months it will delete them because clearly you no longer want them. You are treating Time Machine as an archive program.. it isn't.. it is a backup.. that retains some history.
Recovery software is almost useless for recovery of TM backups. Only if you deleted a prior sparsebundle are you going to have any success and it is extremely unlikely.
There is no way to mount the TC disk locally.. you have to pull it out of the TC. Get a USB holder and plug it into the computer.. the recover data utility can then check for deleted files that still exist. HOWEVER inside a sparsebundle is a whole different story.
Even sending it to a data recovery centre.. I am not sure they will have any success.. if you copied the pictures to the TC and accidently deleted they can be recovered.. but not if you have deleted them (however that happened) inside a sparsebundle.
Mount the TC disk in finder again and check if you have a second sparsebundle..